miniSCP/docs/gotchas.md

# Gotchas — landmines this codebase has already stepped on

Every one of these caused a real bug or debugging spiral. Read before
touching the adjacent code.

## Angular (v22, zoneless, signals, OnPush)

- **Never consume push streams through signal+effect.** An effect that reads
  a signal and (directly or transitively) writes signals re-triggers itself —
  this froze the entire app on the first transfer. Push messages
  (transferUpdate etc.) go through plain callback registries in RpcService.
  Signal coalescing would also silently drop intermediate progress snapshots.
- **No signal writes during template render** (NG0600). Anything that loads
  panels from code paths reachable during render defers with
  `queueMicrotask` (see `PanelsService.newWorkspace`).
- **`[value]` on `<select>` is applied before `@for` options render** and
  silently selects nothing. Use per-option `[selected]` bindings (connection
  manager stack picker).
- Template bindings with special characters: `[class.bg-primary/15]` works;
  `[class.shadow-[...]]` (brackets) does NOT parse — use `[style.box-shadow]`.
  Static class attributes may use arbitrary values freely.
- Functions called from templates ARE reactive: signals read inside them
  register on the view's consumer (call-stack-based tracking). That's why
  `iconClass(entry)` reacting to `settings.iconColors()` works.
- Dedicated tools > shell: IDE diagnostics between paired template/class
  edits are often stale mid-sequence — trust `bun run build:ui` (full AOT
  type-check), not the first red squiggle.
- Tailwind v4 canonical class names: `wrap-break-word` not `break-words`,
  `accent-primary` not `accent-[var(--primary)]`, `z-60` not `z-[60]`.
  Every color used in a template must resolve through `@theme inline`.

## Electrobun

- **Window `close` is not cancellable** (response type `{}`; only the
  app-level `before-quit` supports `event.response = {allow:false}`). All
  unsaved-state guards must either intercept app-controlled close paths
  (⌘W, buttons) or survive the close (editor draft mirroring).
- **One rpc instance per window** — BrowserView binding steals the rpc's
  transport; a shared instance silently sends to the wrong webview.
- **RPC before socket open is silently lost.** Everything gates on the
  socket-open promise (RpcService `ready`).
- The emitter has no `off()`. Window event closures must not capture records
  you want garbage collected.
- `electrobun build` defaults to the **dev** channel; release builds need
  `--env=stable`. The stable app name differs from the dev one
  (`miniSCP` vs `miniSCP-dev`), including the app-data dir implications when
  testing.
- Tray: never call `setImage` after construction on macOS — the template
  treatment is lost and the icon renders black on dark menu bars.
- `ApplicationMenu` is macOS-only in our usage; accelerators on Windows are
  single-character only.
- **`ContextMenu.showContextMenu` is a silent no-op on Linux** (electrobun's own
  `dist/api/bun/proc/linux.md` says so; the app also prints "Application menus are
  not supported on Linux" at boot). Because the UI suppresses the webview's own
  right-click menu, that left EVERY panel context menu dead on Linux — no error,
  nothing happens. The menu is plain HTML now (`ui/src/app/context-menu.ts`) on
  every platform; don't reintroduce the native one for "nativeness" on mac/win
  without keeping a Linux path.

## Linux

- **`ERR_DLOPEN_FAILED` on `bun run start`** means a missing system library, not
  broken app code. `libNativeWrapper.so` links `libayatana-appindicator3.so.1`
  *hard* (for the tray), so the app cannot start at all without it — even though
  the tray is a minor feature. Diagnose with
  `ldd build/dev-linux-x64/*/bin/libNativeWrapper.so | grep 'not found'`; the
  `libasar.so => not found` line in that output is a red herring (it ships beside
  the wrapper and resolves at load). Install list per distro is in
  [platform-notes.md](platform-notes.md).
- Benign startup noise on Linux — all non-fatal, the app runs normally:
  `X11 Error: GLXBadWindow (code 170)`, `Failed to create GBM buffer of size
  WxH: Invalid argument` (compositor/GLX chatter from the GTK webview), and
  `libayatana-appindicator is deprecated. Please use libayatana-appindicator-glib`
  (upstream electrobun's choice, not ours).
- **Window-open flash prevention is three-layer** — remove any one and the
  white/inverted blink returns: (1) windows are created `hidden: true` and
  revealed by `showWhenReady` on the webview's first `dom-ready` (800 ms
  fallback), (2) the bun preload bakes the persisted `data-theme`/tone/accent
  attributes before first paint (`buildPreload`), (3) `ui/src/index.html`
  carries an inline `<style>` with the html background per theme — its oklch
  values MUST stay in sync with the `--background` tokens in styles.css.
- Dev vs prod URL: `getMainViewUrl()` resolves the ng-serve dev server only
  when `DEV_SERVER_URL` is set AND the updater channel is `dev` AND the
  server answers a HEAD request; secondary windows must reuse the resolved
  URL, never hardcode `views://`.
- Upstream Bun panic (`FFI_Callback_threadsafe_call` → `web_worker.spin`):
  rare segfault under long sessions; upstream electrobun×Bun issue, restart
  recovers, nothing app-side to fix.

## Domain logic

- **sessionId ≠ filesystem identity.** Two panels on the same server are two
  SSH sessions. Every same-file/nested-path guard compares `fsKey`
  (`resolvedIP:port` / `"local"`); comparing sessionId caused a
  truncate-to-zero data-loss bug. When fsKeys differ but paths collide, the
  probe-file check unmasks aliased hosts. Never "simplify" this back.
- `createWriteStream` truncates BEFORE the source is read — that's why
  self-copy is destructive, and why guards must run before any stream opens.
- The synthetic `'..'` row: type `'dir'`, must be excluded from selection,
  targets(), filtering match-count, kind/rights/owner display, and drag
  sources. Any new row-level feature must decide what `'..'` does.
- `Semaphore.wake()` must reserve slots synchronously; waking waiters that
  increment asynchronously loses budget under concurrent release.
- Settings: the backend spread-merges (`{...DEFAULT_SETTINGS, ...data}`) so
  new keys auto-default, but the UI SettingsService reads field-by-field —
  a new setting silently stays at default until wired in all five spots.
- The editor draft mirror sends full content per tick (2 MB cap upstream);
  don't shrink the 400 ms debounce.
- `panel.touched` gates localDir auto-navigation; `connectToken` guards
  against a slow connect resolving into a panel the user already reused.

## i18n

- **Translations live in `src/shared/i18n/*.ts` (TS, not JSON)** — deliberate:
  it sidesteps `resolveJsonModule` differences between the Angular esbuild and
  Bun builds and gives full typing. `en.ts` is the source of truth; other
  locales are partial and fall back to English then the raw key.
- **`i18n.t()` is reactive because it reads the `locale` signal** — that's what
  makes live language switching work with no pipe. If you cache a translated
  string in a plain field it WON'T update on switch; call `t()` in the template
  (or in a signal-reading getter) instead. Same for `i18n.date()/size()`.
- Dictionary values are TS string literals: **French/other apostrophes break
  single-quoted entries** (`'…c'est…'`). Use double quotes for any value
  containing an apostrophe. Plurals are `{ one, other }` maps (not ICU strings);
  zh/ja supply only `other`.
- **Native menus can't use the Angular service** — `menu.ts` goes through backend
  `i18n.ts`, and the app menu must be rebuilt when the locale changes (wired in
  index.ts `settingsChanged`), or it keeps the old language. The context menu no
  longer has this problem: it is Angular now and reads `I18nService` directly.
- `eu`/`zh`/`ja` are AI drafts pending native review (see the i18n README).
- **Silent auto-refresh must snapshot sessionId+cwd and discard a mismatched
  result.** A normal `refresh()` is masked by `busy` (input blocked), but the
  silent variant (poll/watch) runs while the user can navigate — without the
  guard, a poll that started in dir A resolves and stamps A's listing over the
  dir B the user just opened. It also never calls `scrollCursorIntoView`
  (scroll must stay put) and returns early if `busy()` or already refreshing.

## Build / tooling

- Angular CLI rejects Bun's Node-compat version — `scripts/node-version-shim.ts`
  is preloaded via `bunfig.toml` at the root AND in `ui/`. Removing either
  breaks `ng`.
- ssh2's optional native deps must stay `external: ["cpu-features", "*.node"]`
  in `electrobun.config.ts` — bundling them breaks the build; ssh2 falls back
  to pure JS at runtime.
- `bun run --cwd ui build` (flag order matters; `bun --cwd ui run build` does
  not do what you want).
- `version.gen.ts` is gitignored and regenerated by postinstall + every build
  script; a fresh checkout fails `tsc` until `bun install` (or any script)
  has run once. Never commit it — it would bump the commit count it records.
- Icon pipeline is `scripts/gen-icons.ts` (resvg) — regenerate after touching
  `assets/logo.svg` or `assets/tray/tray-glyph.svg`; the .ico and tray PNGs
  are build inputs, not build outputs.